Well, I finished The Difference Engine.
I get the impression that some (maybe most) fans of alternate history are in it for the worldbuilding, and can excuse a thin plot or weak characterization if that worldbuilding is really robust. I'm a plot guy, first and foremost, and enjoy worldbuilding as a setting for a good story, but not an end in itself.
This book, though, doesn't really offer a good plot or particularly compelling worldbuilding.
England and the world are different in the late 19th and early 20th century, with the British Empire being the foremost power on the globe, apparently due to the impact of Charles Babbage's mechanical computing technology, the titular difference engine.
The world's version of the United States is actually multiple warring countries, including the United States (which appears to mostly be the union states which lost the US Civil War), the Confederate States, Texas and California.
Other countries are generally reduced in stature as the British Empire overwhelms most of the globe, including summarily winning the Crimean War.
But none of this really matters in terms of the story, which is wafer thin, less than a short story's worth of plot stretched over 400 pages. I've seen this described as a "historical thriller," which feels wildly optimistic. (There's a primitive version of a surveillance state powered by the difference engine, but that's mostly set dressing.)
Very little happens, the central MacGuffin that the featured characters nominally care doesn't really impact anything (and is kind of goofy to begin with) and the characters don't really grow or change, although one moves to France.
Instead, I got the strong impression of Stephenson and Gibson sitting beside me, frantically elbowing me in the ribs gleefully: "Lord Byron is Prime Minister! Isn't that cool? Disraeli is a journalist! There's no such thing as Nelson's Column!" I'm not a Briton, so none of that is personally impactful to me, but I suspect it'd be a big "so what," even if I was.
In lieu of a plot, we get long descriptions of what it's like to visit a prostitute in London during the Big Stink, which isn't particularly interesting or sexy, but just sad, although it definitely feels like Stephenson and Gibson were titillated while writing it.
The worst part, though, is after choosing to not explain
how the difference engine changed the world until the last chapter of the book, the answer turns out to be
underpants gnomes. There's no real explanation for any of why the world is different, other than the Industrial Revolution turmoil with the Luddites was extremely vicious and brought England into a de facto state of civil war.
Why did this break apart the United States? It just did.
Why is Ada Lovelace a practically catatonic drunk who, we're told, has sex with every nobleman in England and appears to be working all sides of the political divide? She just is.
In fact, the writers dwell disapprovingly on the sex lives of single women quite a bit in this novel, in a tone that suggests that it's their point of view, rather than representing societal mores of the world they create.
I see this won a ton of awards when it came out, but I have to imagine a lot of that was due to its pedigree and its novelty, as it predates most steampunk works.